The investigation into rheologic properties of human chorioamniotic membranes has enabled us to appreciate a difference in stress tolerance between term and preterm membranes. The basis for this finding was the application of recurrent amplified pressures in an experimental setting employing a piece of human chorioamniotic membrane obtained immediately after delivery and processed in an apparatus designed for assessment of such pressure application. Our future endeavors will attempt to study fatigue tolerance of these membranes by applying recurrent pressure stresses in an unamplified fashion to the point of fracture. A further correlate of our investigation will be biochemical assessment of connective tissue components specifically collagen and hydroxyproline contained in all membranes studied and correlate these findings with the rheologic properties appreciated in our other investigations. This will be an accumulative attempt to correlate physical and biochemical properties to appreciate the significant clinical problem of premature rupture of the human chorioamniotic sac.